1. Field of the Invention
The present invention relates to a scanning probe microscope such as a scanning capacitance microscope (ScaM).
2. Description of the Related Art
A prior art scanning probe microscope includes a conductive probe unit which is constructed by a cantilever and a probe at its free end (see: JP-A-8-54403). The cantilever is adapted to be approximately in parallel with a surface of a sample, and the probe is in proximity to the surface of the sample. In this case, the cantilever associated with the probe is made of monocrystalline silicon covered by silicon oxide or silicon nitride and metal coated on the monocrystalline silicon. Thus, the cantilever serves as a spring. This will be explained later in detail.
In the above-described prior art scanning probe microscope, however, since the coated metal of the cantilever is so thin that the coated metal has a high impedance, i.e., a low conductivity, the sensitivity of a sensor connected to the probe is substantially decreased. Also, since the coated metal of the cantilever has a larger surface to create a large stray capacitance between the cantilever and the sample, a signal generated from the probe is suppressed by the large stray capacitance. Further, since the radius of curvature of the tip portion of the probe is large, the spatial resolution cannot be increased. In order to increase the spatial resolution, the coated metal has to be made thinner to decrease the radius of curvature of the tip portion thereof; however, this further increases the impedance of the coated metal. In addition, the coated metal is easily peeled off by the friction between the coated metal and the sample. Further, Joule heat generated stays at the tip portion of the probe to dissolve the coated metal at the tip portion of the probe. Thus, the conductivity of the coated metal is decreased.